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Vol. 86
Finally, the free amino sugars and their N-acetyl in a water-cooled quartz immersion well. Product derivatives synthesized chemically or enzymatically isomer ratios were estimated by characteristic abwith enzymes from E . coli strain B, or isolated from sorption peaks in the infrared and/or n.m.r. spectra. C.violaceurn, had identical mobilities on paper chromaResults of a typical run (510 mg. of o-di-t-butylbenzene tography in five solvent systems. in 1 1. of ether) are summarized in Table I, from which As in the case of E . coli strain E’-10, the large amount it is noted that the first stage of the isomerization was of TDP-4-acetamido-4,6-dideoxy-~-glucose found in complete in about 70 hr. Likewise, starting from either E . coli strain B is presumably a reflection of the inm- or p-di-t-butylbenzene, the same photostationary ability of this strain to utilize the nucleotide for polycomposition was reached. Unfortunately, considersaccharide synthesis. E . coli strain B and C.violaceurn able amounts of unidentified by-products were also (which contains viosamine in its lipopolysaccharide) formed, and the total yield of mixed di-t-butylbenzenes are unusual in containing 4-amino-4,6-dideoxy-~-glu-after 75 hr. was found to be only about 2Uy0 as esticose, since 14 other strains of enteric bacteria which have mated by n.m.r. analysis been examined are able to synthesize only the sugar with TABLE I D-galacto configuration. PHOTOCHEMICAL ISOMERIZATION OF O-DI-l-BUTYLBENZENE IN Acknowledgment.-We acknowledge Grant No. GM ETHER 11520 of the National Institutes of Health, Division Time, h r Composition of isomeric Estimation di-1-butylbenzenes of General Medical Sciences, a t Wayne State Univermethod orlho mela Para sity; Grant No. AM 01158 of the National Institutes 0 100% ... ... of Health and G 18742 of the National Science Foun6 80 20 % Traces Infrared dation at Washington University and the University of 18 Infrared 60 30 10% Wisconsin; and Grant No. AM 07588-01 of the 41 15 55 30 Infrared National Institutes of Health a t Nagoya University. 5 50 45 64 Infrared (8) Kational Science Foundation Predoctoral Fellow (9) National Institutes of Health Postdoctoral Fellow.
76 112 146 158
.. ... ...
50 30 20 20
50 70 80 80
Infrared S.m.r. N,m.r. N.m.r.
DEPARTMENT OF CHEMISTRY CALVINL. STEVEXS WAYNESTATEUNIVERSITY PETERBLUMBERGS ... DETROIT,MICHIGAX FRANCIS A . DANIHER~ DEPARTMENTS OF PHARMACOLOGY The same type of photoisomerization also occurs with WASHINGTON UNIVERSITY JACK L. STROMINGERo-t-butyltoluene, but a t only one-fifth the above rate. ST LOUIS,MISSOURI M . MATSUHASHI However, after 36 hr. of irradiation, no isomerization UNIVERSITY OF WISCOXSIN D N. DIETZLERg could be detected with 0- and m - ~ y l e n ep-t-butyltolu,~~ MADISON, WISCONSIN When O F CHEMISTRY SAKARU SUZUKI ene, o-terphenyl, and 1,3,5-tri-t-butylbenzene. DEPARTMENT FACULTY OF SCIENCE TUNEKO OKAZAKI a substituent such as nitro,’ a ~ e t y lor , ~ methoxy15 was h TUNIVERSITY ~ ~ ~ ~ KAZUNORI ~ SUGIMOTO present in the 4-position of 1,2-di-t-butylbenzene, the NAGOYA, JAPAN REIJI OKAZAKI isomerization was strongly inhibited. RECEIVED MAY19, 1964 In another experiment, irradiation of a mixture of t-
Photochemical Isomerization of Di-t-butylbenzenes Sir: As an extension of our studies on the chemistry of o-di-t-butylbenzene, we have examined the photoirradiation of this hydrocarbon. In contrast to the conversion of 1,2,4-tri-t-butylbenzene into a substituted bicyclo [2.2.O]hexadiene (Dewar-type “benzene”) on irradiation in ether solution with a mercury arc lamp through a Vycor filterj2 o-di-t-butylbenzene when similarly irradiated in an all-quartz apparatus3 undergoes a new kind of isomerization to form a 1 :4 photostationary equilibrium mixture of m- and p-di-t-butylbenzene.4,4a Irradiations in our work were conducted in dilute ether solution, under nitrogen, with a 100-watt Hanovia Type SA36 quartz-jacketed mercury light source placed (1) A. W. Burgstahler, M. 0. AbdebRahman. and P. L. Chien, Telrahedron Lellers, 61 (1964). (2) E. E. van Tamelen and S. P. Pappas, J . A m . Chem. Soc., 84, 3789 (1962). (3) With the use of a Vycor filter (No. 7913),only unidentifiable products, which darkened rapidly in air, could be obtained. (4) After communication of these results t o Professor van Tamelen, we were grateful t o learn t h a t he also has obtained similar findings in t h e photoirradiation of o-di-1-butylbenzene. (4a) NOTE ADDED IN PRooF.-Since submission of this paper, related photoisomerizations of other dialkylbenzenes have been reported by K. E. Wilzbach and I-. Kaplan [ J . A m . Chem. S O L . , 86, 2307 (196411. Using a much higher intensity light source, these workers observed isomerizations of o- and m-xylene which we have not been able t o detect under our conditions, even after prolonged irradiation
butylbenzene and 1,3,5-t-butylbenzene failed to yield any detectable amount of di-t-butylbenzenes. Likewise, even after prolonged irradiation, none of the dit-butylbenzenes showed any tendency to disproportionate into mono- and tri-t-butylbenzene,6 Consequently, these photochemical isomerizations appear to be intramolecular in nature. When the photoirradiation of o-di-t-butylbenzene was conducted in olefin-free petroleum ether (b.p. 35-40’), the rate of formation of m- and p-di-t-butylbenzene was much slower than in ether, and considerable amounts of colored by-products were also produced. Other experiments with photosensitizers’ such as benzophenone revealed little dependency of the isomerization on the presence of such substances. Mechanistically, these isomerizations can be accounted for either by photoinitiated 1,2-migrations of a t-butyl group or by excitation of the benzene ring to a Ladenburg-type structure with subsequent rearomatization to form the metu and thence the para isomer. We hope to distinguish these two possibilities by appropriate ring labeling with CI4, since there is no actual carbon-carbon migration of a t-butyl group in the latter pathway. ( 5 ) Preparation described in t h e Ph.D. thesis of P. L. C., University of Kansas, 1964. (6) Such disproportionation is well known in Friedel-Crafts reactions of di- and tri-1-butylbenzenes. Cf. P. D. Bartlett, M. Roha, and R . M. Stiles, J . A m . Chem. S O L . ,76, 2349 (1954). (7) Cf.J . Saltiel and G. S. Hammond, i b i d . , 86, 2515 (1963).
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Acknowledgment.-We are grateful to Professor Earl S. Huyser for the use of the quartz irradiation apparatus and lamp. We also thank the Alfred P. Sloan Foundation and the National Science Foundation for generous financial support of this work. (8) Alfred P. Sloan Research Fellow, 1961-1964.
ALBERTW. BURGSTAHLER~ DEPARTMENT OF CHEMISTRY UNIVERSITYOF KANSAS PING-LUCHIEN LAWRENCE, KANSAS RECEIVED MAY26, 1964
Eight-Coordinate Complexes of Cobalt(I1). A Principle Influencing the Occurrence of High Coordination Numbers' Sir: Several years ago, compounds containing the tetranitratocobaltate(I1) ion, [Co(N03)4l2-, were reported from several l a b o r a t o r i e ~ . ~On ~ ~ the basis of its magnetic moment and its visible and infrared spectra, this complex ion was assigned a tetrahedral structure. However, as a result of subsequent inv e s t i g a t i o n ~ ~of, ~ the compounds Co(R3M0)2(N03)2, R = CH3 or C6H5, M = P or As, i t was suggested that bidentate nitrate ions might also occur in [Co(N03)4]2-with the over-all arrangement of oxygen atoms about the metal ion being such as to produce a ligand field of approximately tetrahedral symmetry, even though the actual disposition of oxygen atoms would not have this shape. We wish to report that a single crystal X-ray structure determination of [As(C6H5)4I2[Co(NOa)4] demonstrates that this is indeed the case, each nitrate ion being bidentate, and the Co(11) being eight-coordinate in a dodecahedral complex. The complex was prepared by mixing stoichiometric quantities of As(CeHJ4Cl, AgN03, and CoCl? in acetonitrile. After separating the insoluble AgCl by decantation, the solution was condensed to an oil by evaporation, and the remaining acetonitrile was extracted into ether. The complex was then recrystallized from a chloroform solution by addition of cc14. The unit cell is monoclinic, a = 23.47, b = 11.34, c = 18.57 A,, /3 = 107', and contains two formula units. The space group is C2/c and the cobalt atoms occupy special positions requiring the [Co(N03)4lZ- ions to have CZsymmetry axes. The eight oxygen atoms surrounding the cobalt atom lie a t the vertices of a distorted dodecahedron. Figure 1 shows some of the important bond distances and interbond angles a t the present stage of refinement, in which only isotropic temperature factors have been used. The complete structure can be obtained by rotating each of the nitrate ions shown about the C2 axis. Within the limits of error, the [Co(N03)4]*-ion has only CZ",rather than D 2 d symmetry, but it is useful to divide the eight Co-0 bonds into just two sets. In one, consisting of bonds from Co to 01 and OIV, the Co-0 distances are in the normal range for Co-0 bonds, 2.02 and 2.05 A.; in the other set of bonds, from Co to 011 and OV, they are much longer, 2.41 (1) Research supported by a grant from the U. S. Army Research Office. (2) F . A. Cotton and T. G . Dunne, J . A m . Chcm. S o c . , 84,2013 (1962). (3) D . K.Straub, R. S. Drago, and J. T. Donoghue, Inorg. Chem., 1, 848 (1962). (4) F.A. Cotton and R. H. Soderberg, J . A m . Chcm. SOL, 86, 2402 (1963). ( 5 ) F.A. Cotton, D . M. L. Goodgame, and R . H. Soderberg, Znorg. Chem., I,1162 (1963).
Figure 1.
and 2,69 A , but still short enough to indicate a definite Co-0 bonding interaction. The four short bonds approximately define an elongated tetrahedron with a vertical angle of 45-50', while the four long ones define a severely flattened tetrahedron-very nearly a square-with a vertical angle of about 170'. It has also been found that an analogous compound containing (CF3COO)- in place of (ONO2)- can be prepared, viz., [AS(C~H~)~]?[CO(~~CCF~)~]. This has essentially the same spectrum and magnetic moment as the nitrato complex. It crystallizes in the tetragonal system, space group 141/a, a = 11.68 A., and c = 40.82 A., with four formula units per cell. I t is thus required that the Co atoms lie a t special positions with ;? symmetry and this makes it seem likely that the [Co(OZCCF3)4]*-ion has an eight-coordinate structure similar to, but more regular than, that of [Co(N03)4I2-, although this is not absolutely required. A thorough investigation of the structure is in progress. We believe that from the above results and other data in the literature, an interesting and useful structural principle may be inferred, namely, that a polyatomic ligand in which two chemically equivalent atoms are held much closer together than such a pair of atoms would be if independent of each other has a tendency to interact through both of the equivalent atoms in such a way that the mean positions of the pairs of atoms lie roughly a t the vertices of one of the usual (e.g., octahedral or tetrahedral) coordination polyhedra. This is a generalization of the earlier suggestion5 that in the C O ( R ~ P O ) ~ ( N Ocompounds, ~)? each nitrate ion as a whole occupies a vertex of a distorted tetrahedron about the cobalt ion. In the [Co(NO3)4l2-ion, this tendency is manifested in the fact that all four of the nitrate ions present two oxygen atoms to the cobalt ion, and the centers of the nitrate ions (the N atoms) lie a t the vertices of a flattened tetrahedron, the two N-Co-N angles bisected by the molecular CZ axis being 152 and 144'. However, if lines are drawn to points along the 0 . 0 lines within nitrate ions, such that these points lie a t distances from each oxygen atom which are inversely proportional to the distances of the oxygen atoms from the cobalt atom, angles between these lines are very
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